Bearsden Bio, Inc. is developing novel research kits for sale to the scientific community through its Cruachem division and is developing a technology based on regulating protein expression at the RNA level. The overall goal of this SBIR program is the development and commercialization of a method for the preparation of quantities of proteins containing unnatural amino acids at single, predetermined sites. For Phase I, we plan to demonstrate the feasibility of establishing an efficient, robust method for the elaboration of such proteins. This is to be done by realizing two specific aims, namely 1. Demonstration of the applicability of a novel protecting group to a broad cross of aminoacylated tRNAs. 2. Realization of an increase in the yield of proteins prepared by in vitro translation, where introduction of an unnatural amino acid involves suppression of a nonsense codon with a misacylated suppression tRNA. Completion of this progrartant modifications for understanding protein function. PROPOSED COMMERCIAL APPLICATION: The final development of a robust, efficient misacylated synthesis system will benefit Bearsden in two ways: as a novel kit for sale to the research community and as an enabling technology for use in drug discovery. The latter will represent an important advance in ArnaX Integrated Rational Drug Discovery program as it enables a more thorough understanding of RNA Binding Proteins and other pharmacologically important proteins.